Watercore Incidence in `Red Delicious' Apple in Relation to IAD Values: Effect of Harvest Date, and Harvista and Retain Applications

`Red Delicious’ is susceptible to watercore development during maturation and ripening on the tree. Maturation as indicated by I_AD values, starch pattern indices and internal ethylene concentrations (IECs), and the incidence and severity of watercore at the time of harvest and during cold storage, have been studied  in relation to harvest date and use of the pre-harvest plant growth regulators (PGRs)1-methylcyclopropene (1-MCP; Harvista) and aminoethoxyvinylglycine (AVG; ReTain). Freshly harvested fruit were sorted into I_AD values of 0.2 to 1.8 in 0.2 unit increments and then stored in air at 0.5^oC and 85% RH for 7 months. PGR applications decreased watercore incidence and severity relative to untreated fruit, and showed good correlations with IECs up to week 10 of storage. I_AD values, IECs and watercore severity were poorly related after 28 weeks of storage both in non-treated and treated fruit.  Fruit without PGR treatment harvested one week earlier had lower IECs than either treated or non-treated fruit harvested a week later, but with the same degree of watercore disappearance after 28 weeks of cold storage. The DA meter may be useful for predicting fruit maturity and possible watercore severity at the time of fruit harvest, but disorder disappearance in long-term cold storage was more influenced by the date of fruit harvest.

We thank NY Apple Research and Development Program and AgroFresh Inc., and USDA National Institute of Food and Agriculture, Hatch project 2013-14-483, Non-destructive measurement of apple maturity for funding the project. Also, the financial assistance of Tarbiat Modares University (TMU) to the first author for his living cost during sabbatical leave at Cornell University is acknowledged.